Abstract 11615: The Prevalence and Association of Exercise Test Abnormalities With Sudden Cardiac Death and Transplant-Free Survival in Childhood Hypertrophic Cardiomyopathy

Introduction: Hypertrophic cardiomyopathy (HCM) can be associated with an abnormal exercise response. In adults with HCM, an abnormal exercise stress test (EST) is predictive of heart failure outcomes. Our goal was to determine if an abnormal exercise response is associated with adverse outcomes in pediatric HCM patients. Methods: : In an international cohort study with 20 centers (PRIMaCY), children <18 years with primary HCM were included. Abnormal EST was defined as an abnormal heart rate or blood pressure response, arrhythmias and/or ischemic ECG changes on exercise. Sudden cardiac death (SCD) events were defined as a composite of SCD and aborted SCD including appropriate implantable cardioverter defibrillator discharges. Using Kaplan-Meier survival analyses, we analyzed the association of abnormal EST with SCD and transplant-free survival. Results: Of 724 eligible patients, 604 underwent at least one EST on follow-up. There were no differences in clinical characteristics between those with or without an EST. The median age at EST was 13.8yrs (IQR 11.0-15.7yrs), 76% were male, 55% were on beta-blockers. 299 (49.5%) had an abnormal EST. Patients with an abnormal EST had more severe septal hypertrophy, higher left atrial diameter z-scores, higher resting LV outflow gradient at first evaluation, and a higher proportion were genotype-positive (p<0.05) compared to those with a normal EST. An abnormal EST was associated with lower 5-year transplant-free survival (99% vs. 95%, p=0.0082) and lower 5-year freedom from SCD events (96% vs. 92%, p=0.025) (Figure 1). Conclusions: Exercise abnormalities are common in childhood HCM. An abnormal EST in children with HCM was associated with lower transplant-free survival and more SCD events. Further analysis will determine if the inclusion of EST results can increase the predictive accuracy of current pediatric SCD risk prediction models.